Re: Anomalous Difference in Output between HTML Files Created by 'cover'

[leif . eriksen]

I'd guess it is because you are seeing the output of the code after it 
has been compiled-then-decompiled - it is compiled so it can run and 
coverage statistics can be collected, then it is decompiled to relate 
coverage stats to code lines. Now there are many ways to write code that 
compiles to the same compiled form, but the decompiler (I imagine it is 
B::Deparse) only decompiles those symbols one way.

As a test, you could change those two lines in Text::Template to be the 
same as what you are seeing in the coverage HTML, run the make test and 
cover again and see them unchanged.

Or more directly
===========
deparse.pl
===========
#!/usr/bin/perl -w
use strict;
my $self;
$self->{DATA_ACQUIRED} = 1;
+++++++++++
end deparse.pl
+++++++++++
prompt> perl -MO=Deparse deparse.pl
BEGIN { $^W = 1; }
use strict 'refs';
my $self;
$$self{'DATA_ACQUIRED'} = 1;
deparse.pl syntax OK
===========
deparse2.pl
===========
#!/usr/bin/perl -w
use strict;
my $self;
$$self{DATA_ACQUIRED} = 1;
+++++++++++
end deparse2.pl
+++++++++++
prompt> perl -MO=Deparse deparse2.pl
[EMAIL PROTECTED] perl]$ perl -MO=Deparse deparse2.pl
BEGIN { $^W = 1; }
use strict 'refs';
my $self;
$$self{'DATA_ACQUIRED'} = 1;
deparse2.pl syntax OK
Leif
[EMAIL PROTECTED] wrote:
I have just noticed an anomalous difference in output between two of 
the files created by the Devel::Cover 'cover' utility when run against 
a popular Perl module -- and I am wondering whether this difference 
should be considered a feature or a bug.

The module in question is Text::Template, which I am studying as part 
of Perl Seminar NY's contribution to the Phalanx project.  Start with 
a copy of Text-Template-1.44 (the latest on CPAN) and examine the 
code. In 'lib/Text/Template.pm', consider these two lines:

  128    $self->_acquire_data unless $self->{DATA_ACQUIRED};
  450        if (! defined $val) {
Proceed in the normal manner:
  perl Makefile.PL
  make
  cover -delete
  HARNESS_PERL_SWITCHES=-MDevel::Cover make test
  cover
... 'cover' creates a number of HTML files, including these two:
  ./Text-Template-1.44/cover_db/blib-lib-Text-Template-pm.html
  ./Text-Template-1.44/cover_db/blib-lib-Text-Template-pm--branch.html
'blib-lib-Text-Template-pm.html' displays lines 128 and 450 exactly as 
they appear in the module itself. 
'blib-lib-Text-Template-pm--branch.html', however, displays the 
relevant branch part of these lines of code as follows:

  128  unless $$self{'DATA_ACQUIRED'}
  450  if (not defined $val) { }
'$self->{DATA_ACQUIRED}' is changed to '$$self{'DATA_ACQUIRED'}' and 
'! defined $val' is changed to 'not defined $val'.  (I could site 
other examples as well, but these suffice to illustrate the point.)

Now, I grant that these are merely displays, not live code. 
Nonetheless, since the purpose of these HTML files is to guide a 
programmer to lines of code whose test coverage needs improvement, I 
am puzzled as to why the output in these two files differs.

Jim Keenan